Method of removing aluminum from barium sulfide solutions

ABSTRACT

ALUMINUM OXIDE IMPURITIES ARE REMOVED FROM AGUEOUS BARIUM SULFIDE SOLUTION BY CONTACTING THE SOLUTION WITH ANHYDROUS MAGNESIA-CONTAINING SOLID PARTICLES. THE ALUMIMUM OXIDE IMPURITY IS REDUCED BELOW 0.02 GRAM/LITER BY THIS TREATMENT. THE PREFERRED MAGNESIUM OXIDE MATERIAL IS CALCINED MAGNESITE IN A PARTICLE SIZE SMALLER THAN 200 MESH. THE MAGNESIUM OXIDE AND ALUMINUM OXIDE SOLIDS ARE SEPARATED FROM THE PURIFIED SOLUTION BY FILTERING OR CENTRIFUGING THE MIXTURE.

July 13, 1971 v, R, HORN 3,592,589

METHOD OF REMOVING ALUMINUM FROM BARIUM SULFIDE SOLUTIONS Filed March 18, 1969 3 Sheets-Sheet l.

24 FEED STEAM CONDENSATE SEPARATOR j IMPURITIES PURIFIED BaS SOLUTION Figql INVENTOR. VERNON R. HORN Wy y ATTORNEY July 13, 1971 v, HORN 3,592,589

METHOD OF REMOVING ALUMINUM FROM BARIUM SULFIDE SOLUTIONS Filed March 18, 1969 3 Sheets-Sheet a 5 MIN.

I5 MIN.

l I I l l l 4=I 8:! I2! I62! 20:! 281! 40 i WEIGHT RATIO MgO N 0 Fig.2

INVENTOR. VERNON R. HORN ATTORNEY V. R. HORN July 13, 1971 METHOD OF REMOVING ALUMINUM FROM BARIUM SULFIDE SOLUTIONS Filed March 18, 1969 5 Sheets-Sheet 5 8 5 mum TREATMENT TIME (HRS) Fig. 3

INVENTOR. VERNON R. HORN ATTORNEY United States Patent Office 3,592,589 Patented July 13, 1971 US. Cl. 23134 Claims ABSTRACT OF THE DISCLOSURE Aluminum oxide impurities are removed from aqueous barium sulfide solution by contacting the solution with anhydrous magnesia-containing solid particles. The aluminum oxide impurity is reduced below 0.02 gram/liter by this treatment. The preferred magnesium oxide material is calcined magnesite in a particle size smaller than 200 mesh. The magnesium oxide and aluminum oxide solids are separated from the purified solution by filtering or centrifuging the mixture.

BACKGROUND OF THE INVENTION In the manufacture of barium hydroxide and barium carbonate from baryte ores, the raw material (principally barium sulfate) is heated with carbon to produce black ash. By leaching the black ash with hot Water, barium sulfide is recovered as a leach liquor along with several impurities. Subsequent filtration of the leach liquor will not remove aluminum oxide impurities. In order to prevent the precipitation of undesired aluminum compounds with the barium products made from the barium sulfide leach liquor, it is necessary to purify the leach liquor to remove substantially all of the aluminum impurities. These impurities are believed to be present in the form of soluble barium aluminate, but hereafter are expressed as the oxide Al O Pure barium carbonate or barium hydroxide are useful in the manufacture of ceramics, glasses, electronic components, and as intermediates in the manufacture of various chemical compounds.

BRIEF SUMMARY OF THE INVENTION It has been discovered that substantially complete removal of aluminum impurities can be achieved by contacting the barium sulfide solution with anhydrous magnesia-containing particles. More than 90 wt. percent of the impurity can be removed using a weight ratio of magnesium oxide to aluminum oxide greater than about 4:1.

While partial removal of the impurities can be obtained at lower temperatures, treatment of the leach solution at about 60 C. to 100 C. for about one hour removes all but trace amounts of the impurity. Also, the solubility of barium sulfide in water is much higher at these temperatures than at ambient temperatures. Leach liquor from the black ash leaching operation is usually supplied at 65 C. to 75 C., and most of the examples use this temperature for the treatment for removing aluminum impurities. These concentrated solutions have a specific gravity of about 1.12 to 1.15 and contain about 145 to 175 grams of barium sulfide per liter. By reducing the aluminum impurity content below about 0.02 g./l., pure barium compounds may be produced from the barium sulfide solution by addition of hydroxide or carbonate ions.

Although no definite proof of a specific chemical reaction has been found, it is believed that this treatment converts a soluble barium-aluminum oxide material to an insoluble precipitate.

THE DRAWING FIG. 1 is a side view partially cut away of a typical treatment tank for carrying out the purification on a batch basis;

FIG. 2 is a logarithmic plot of final aluminum oxide concentration vs. MgO:Al O weight ratio for the purification treatment and FIG. 3 is a semi-logarithmic plot of concentration ws. treatment time.

DESCRIPTION In FIG. 1 a treatment tank 10 has a jacketed inner vessel 12 and is fitted with a steam inlet 14 and condensate outlet 16. An agitator 20 is mounted on the tank cover 22 and is powered by a motor 24. The leach liquor tobe purified is passed into the treatment tank 10 through top port 26. The anhydrous magnesia-containing solid particles can be admitted as a dry powder through the same port 26, or as a slurry, or may be premixed with the leach liquor. After the solution has been agitated and held at the treatment temperature for a sufiicient time to assure substantial removal of the impurities, the purified solution and precipitated solids are taken from the treatment tank 10 through drain port 28 and separated as by filtering or centrifuging the mixture. If the particular feed stock liquor requires other treatment, such further treatment may be carried out in the same tank if conditions permit, either concurrently or sequentially with the purification treatment with magnesium oxide material.

While the process is described herein as a batch process, the invention can be modified to achieve a continuous process.

In selecting the magnesia-containing material for use in this invention, several chemical and physical properties of the treating agent should be considered. In order to prevent contamination of the BaS solution, it is preferred that no deleterious ions be introduced with the treating material. There exist several substantially insoluble magnesium compounds which contain the oxide form of magnesium. It is preferred that the treating material have a water solubility of less than about ppm. at the treatment temperature. It is also preferred that the treating material contain no water of hydration.

The mechanism of reaction by which the aluminum impurity is precipitated with the magnesium oxide material is not fully understood. The particle size of the treating material appears to be significant in achieving fast reaction. Calcination of magnesia-containing compounds, such as magnesite, basic magnesium carbonate or magnesium hydroxide, in the temperature of about 900 to 1500 C. produces an essentially pure magnesia (MgO) preferred for use in this invention. Calcined magnesite is commercially available having an average screen size of less than 200 mesh. The finer material (400 mesh or smaller particles) is very reactive. Such material has a loose bulk density of about 200500 grams/liter, with a bulk density of less than 300 g./l. being the better material.

Example I A barium sulfide solution from the leaching of black ash contains grams/liter of BaS and 0.408 g./l. A1 0 impurity. The specific gravity is 1.138 and the treatment temperature is 75 C. The magnesia-containing material is calcined magnesite (Type A) containing 97 to 99 wt. percent MgO. The particle size is suflicient to pass through a 200 mesh screen and the bulk density is about 220 to 270 g./1. The Weight ratio MgO:Al O is 4.9:1, equal to 2.0 grams/liter of the treating agent. The aqueous barium sulfide solution containing the aluminum oxide impurity is contacted with the magnesium oxide particles for one hour while agitating the mixture. The solids are filtered and the purified solution contains 0.013 g./l. A1 equal to 96.5 wt. percent removal of the impurity.

4 mum conditions for economical operation of the purification process. In FIG. 3 a semi-log plot of final aluminum impurity concentration vs. time is given for the Example H ratios of 2:1, 4:1 and 8:1. These data were taken for a A concentrated aqueous BaS solution (sp. gr.=l.l15) 5 treatment temperature Of using yp C containing 0,233 g /1 of A1 0 impurity was tfeatgd f nesia. (calcined magnesite) material as in the reactions 1 hour at 7075 C. with a magnesia-containing material Shown for The aqueous 1335 Solution 1 8 consisting essentially of magnesium carbonate. The treat- Contained about 0-120 t0 0-126 of alumiing agent was commerciany il bl M co (Mi hi num oxide impurity. The extended treatment times had Chem. Co. No. 71009-P-2). By contacting the solution 10 i e effe p impurity removal for the low values of with 3.9 gm. MgCO /liter (equiv. ratio MgO:Al O :8.1) parts s P P 2 3 and even at 8 hours less the impurity was reduced to a concentration of 0.143 g./ l. than 0f the p y Was removed However, at a (64.2% removal). By raising the ratio of treating agent ratio of 8:1 more than 99% can be removed in 8 hours. to impurity, the removal can be improved. Using 7.4 gm. MgCO /liter (equiv. ratio: :1), the impurity concen- 15 Examp 1e Iv tration was reduced to 0.004 g./l. (98.3% removal). Thus, Some aluminum impurity can be removed at ambient the chemical composition of the magnesia-containing temperature; however, it is usually not considered a comtreatment material is seen to have a substantial effect On mercially feasible process because the concentrated BaS the necessary amount of MgO present in the treating leach liquor must be kept at higher temperatures to preagent. vent the BaS from precipitating. During the normal opera- Example I II tion of a black ash leaching plant, the black ash is con- The procedure of Example I was repeated, except that tacled with hot Water. at about to Separate the 2D gJL of reagent grade magnesia (Type B) was used barium from the residue Therefore, 1t 1s convenient to to treat the BaS Solution at C for 2 hours. The treat the saturated leach liquor while maintaining the tem- Solution (Sp. g 11:1-11 5) contained 0214 g A of A1203 perature of the leach eflluent to prevent loss of BaS from impurity which was reduced to 0.124 g./l. by the treattha product Stream exqmp 1e 15 glven.merely to .dqm' ment. Exlen h the relatively high 9 3:1 Weight ratio onstrate that the purlfication of aluminum-containing the pure reagent grade MgO did not equal the perform aqueous BaS .Solutlons p be pelformed at lower temance of calcined material. This suggests that the thermal 3 peratpres' Whlle Speclfic gravlty of a saturated BaS history of the treating agent can be an important con- 0 Solution at ,leachmg teaperatule 1s usually more .than sideration in selecting the material. It is known from prior at 31 the Spec! c gravlty of i Saturated hquor literature that calcining magnesia-containing materials 18 1 about 1074' Type C magnesla was as the from 900 to 1500 C. or higher has a substantial effect on trleatlpg agqnt' After 8 g of if 6 3 i the the crystalline properties and solubility of the calcined aummum lmpunty was ecrqase 6 to 3'.) 0.109 g./l. (19% removal), using a MgO.Al O ratio of product. The effect of varlations 1n the weight ratio of For the same conditions a Wei ht ratio of added magnesia (MgO to aluminum impurity (expressed d th t 0100 A 6%, 1 as A1 0 prior to the purification treatment was studied cfiease e lmpun 0 b1 0 remova 16 over a Wide range of g 2 3 Weights The g g t e newtreatment 1s opera e at am lent temperature, the graph of FIG. 2 plots the efiects of these changes upon 40 process ls extremely slow below about the concentration of aluminum impurity in the treated Examples V-XI BaS solution. This series of experiments was conducted at 01 near the boiling temperature (95l00 C.) of the A number of treatmg agents W aqueous BaS solution which had a specific gravity of 1.115 found to remove alumlflllm de nnpurity with various and contained 0.232 to 0.253 g./l. of aluminum impurity. 4:5 degrees of Success- In Table I these reagents are llsted Th three curves shown i Fla 2 represent a ti Paramand the results of the purification treatment are shown for eter for the period of contact between the BaS solution each treatment. The contact time was 2 hours, and the and MgO-containing treatment material. The treating treatment temperature was -75 C.

TABLE I Cone. BaS gravity w Percent Ex. Treating agent (g./l.) (sp.gr.=g./l.) Before After removal V Mg(OH) (magnesium hydroxide) 2.9 1.120 0.350 .291 16.8 VI CflMg(CO3)z (dolomi 2.0 1.124 .296 .168 43.2 VII-.." CaO MgO (calcined dol0rmte) 2.0 1.126 .365 .255 30.1 VIII MgSOt 7Hz0 (magnesium sulfate). 12.0 1.133 .348 .192 36.8 IX lVIgCzOz 2H2O (magneslum oxalate). 7.4 1.133 348 .103 70. 5 X Mg(NO3)2'6H20 (magnesium nitrate 12. 8 1.133 .348 .107 69. 3 X1 MgO (Type A) 2.0 1.140 .408 .011 96.7

agent (Type C magnesia) was a slightly less reactive form of calcined magnesite than used in Example I (Type A). Type C HgO has a bulk density of about 320-480 g./l. and an average particle size less than 200 mesh. The MgO content of the calcined magnesite was about 97-99%.

As can be seen in the three curves of FIG. 2, impurity removal can be effective with short treatment periods if sufliciently high amounts of MgO are used. More than 90% impurity removal is realized in 5 minutes at the boiling point if the very large ratio of 40 parts MgO per- Weight part of A1 0 is used, while considerably less treating material is needed to effect the same degree of impurity removal at longer contact periods.

The effect of longer treatment times was studied at relatively low MgO:Al O ratios to determine the opti- Examples XIIXV A weight ratio of MgO:Al O less than 4:1 can be used to obtain substantially complete removal of the aluminum impurity; but the increased time required for such removal may be too long for some operations. Table II shows the treatment of a concentrated BaS solution at about 75 C. with Type A MgO in an amount to give a 3.1:1 ratio (0.50 g./l.). The initial impurity concentration was 0.159 g./l. A1

While the process has been described by specific examples, there is no intent to limit the inventive concept except as set forth in the following claims.

What is claimed is:

1. A process for removing an aluminum oxide impurity from an aqueous barium sulfide solution comprising the steps of contacting the solution containing aluminum oxide impurity with finely divided anhydrous magnesia-containing solid material in an amount sulficient to precipitate at least 90% of the aluminum oxide impurity, and separating the barium sulfide solution from the magnesia-containing and aluminum oxide materials.

2. The process of claim 1 wherein a Weight ratio of magnesia to aluminum oxide greater than 4:1 is used and wherein the solution is agitated and heated between about 60 C. and 100 C. for at least 1 hour.

3. The process of claim 1 wherein the magnesia-containing material consists essentially of calcined magnesite having an average particle size smaller than 200 mesh and a bulk density less than about 500 g./l.

4. The process of claim 1 wherein the purified barium 6 sulfide solution has an aluminum oxide content less than 0.02 grams/liter.

5. A process for treating hot aqueous BaS leach solution containing about -175 g./l. BaS for removing an aluminum oxide impurity from the BaS solution which comprises the steps of:

admixing the BaS solution containing aluminum oxide with suflicient magnesium oxide particles to remove substantially all of the aluminum oxide by precipitation;

maintaining contact between the hot BaS solution and the magnesium oxide particles until substantially all of the aluminum oxide impurity has precipitated from the solution; and

separating the BaS solution from the magnesium oxide and aluminum oxide precipitate.

References Cited UNITED STATES PATENTS 648,772 5/1900 Moffatt 23-134 1,856,194 5/1932 Seailles 2352X 2,163,388 6/1939 Wuethrich 23-137 2,605,167 7/1952 OBrien 23134 2,651,563 9/1953 Rentschker 23-186 FOREIGN PATENTS 514,583 11/1939 Great Britain 23186 859,249 l/ 1961 Great Britain 23-186 OSCAR R. VERTIZ, Primary Examiner G. O. PETERS, Assistant Examiner 

